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If the Muon /1/, /2/ have finished (or crashed) the installation then you could kill the Muon. The KDE has graphical System Activity /3/ screen. You could kill processes with it.
The System Activity should ask the root password if it needs it. Sometimes the password query is under the System Activity window. That is, you need to move the System Activity window to see the password query window.
You could also kill the muon process from the command line. Example:
Starting a konsole and typing:
:~$ ps -e | grep muon
2022 ? 00:00:01 muon
:~$ sudo kill 2022
[sudo] password for User:
After this check with the Muon package manager, if there are broken packages or other error messages.